Abstract: A projection-type video display in which the entire input video signal is first digitally corrected through digital gamma correction. Then, a subset of the corrected video signal is corrected again through analogue correction techniques. In particular this portion of the digitally corrected video signal corresponds to the subject where slopes of applied voltage-transmissivity characteristic curve (V-T curve) of liquid crystal changes relatively rapidly. The result is a more accurate gamma correction which is also less expensive than conventional, purely digital gamma correction systems.

Abstract: An A/D converter samples an analog video signal, having a frequency corresponding to various types of image supply apparatus, and converts the signal into a digital signal. A sampling clock signal supply circuit supplies a sampling clock signal to the A/D converter, and comprises an edge detection circuit for adjusting the phase of the sampling clock signal. The edge detection circuit subjects the video signal and a delayed video signal to subtraction processing to generate edge pulses. A processor selects a sampling clock signal of a desired phase based on edge information determined by these edge pulses. The present device can also adjust a threshold voltage that is input to the comparator, and the phase of the sampling clock signal based on a digital signal, and supply a dedicated video signal for phase adjustment from a personal computer.

Abstract: A projection-type video display in which the entire input video signal is first digitally corrected through digital gamma correction. Then, a subset of the corrected video signal is corrected again through analogue correction techniques. In particular this portion of the digitally corrected video signal corresponds to the subject where slopes of applied voltage-transmissivity characteristic curve (V-T curve) of liquid crystal changes relatively rapidly. The result is a more accurate gamma correction which is also less expensive than conventional, purely digital gamma correction systems.